Communication inside a bustling restaurant or other crowded or reverberant location is one of the most difficult tasks for a hearing impaired person. The high level of background noise due to surrounding conversations reduces the signal-to-noise ratio (SNR) for the speech signal from the desired communication partner. Impulse-like noises created by cutlery clanging against plates may cause unwanted reactions in the hearing aid, such as sudden changes in amplification. Restaurants are often decorated with hard surfaces, such as glass partitions between sections of the locality, which are intended to create a sense of privacy, but which also cause highly reverberant conditions with long echo time constants both for the interfering background noise as well as for the speech signal from the desired communication partner.
In order to help improve the hearing capability of a hearing impaired person modern hearing devices provide a number of means to reduce the adverse effects encountered in difficult listening environments such as restaurants. For instance U.S. Pat. No. 3,946,168 discloses a hearing aid with a directional microphone that is capable of emphasizing the speech from the front, i.e. from the direction where the desired communication partner is usually located, thereby increasing the signal-to-noise ratio. Further, U.S. Pat. No. 5,473,701 discloses a method and apparatus for enhancing the signal-to-noise ratio of a microphone array by adjusting its directivity pattern. Alternatively, the communication partner can wear a microphone where the microphone signal is transmitted to the hearing device via a wireless link, with the intention of emphasizing the direct component of the speaker's voice, picked up close to the speaker's mouth, thereby reducing noise and reverberation. Such solutions are for instance disclosed in WO 2005/086801 A2 and EP 1 460 769 A1. As a further means, EP 1 469 703 A2 discloses a reverberation cancelling algorithm that reduces the effect of long echo time constants. Moreover, WO 2007/014795 A2 discloses a method for acoustic shock detection and its application in a system applying anti-shock gain reduction when a shock event has been indicated, for instance to reduce the unpleasant sounds produced by clashing cutlery and plates. As yet a further means, U.S. Pat. No. 6,104,822 discloses a hearing aid providing a plurality of manually selectable hearing programs adapted for a variety of listening situations. A further improvement of such a multi-program hearing device is disclosed in WO 02/32208 A2 where a method for determining an acoustic environment situation is described, which enables the automatic selection by the hearing device of a hearing program suitable for processing the audio input signal in the momentary listening situation. Alternatively, EP 1 753 264 A1 discloses a method for the determination of room acoustics, so that the signal processing in a hearing device can be automatically adapted to the current room acoustics. Moreover, U.S. Pat. No. 7,599,507 discloses a means for estimating speech intelligibility in a hearing aid in order to adjust the settings of the hearing aid. Despite the fact that the existing solutions for improving signal-to-noise ratio and reducing reverberation are effective to some extent, especially when applied in combination, the problem of reduced speech intelligibility under adverse listening conditions, such as encountered in restaurants, remains.
Within a noisy and reverberant environment such as a busy restaurant, some locations will be better suited for a hard of hearing person than others, because the level of background noise or reverberation will be lower than elsewhere. During the fitting and counselling procedure the audiologist or other hearing care specialist will often try to instruct the user of a hearing system on how to select an optimum location in a restaurant. However, such optimisation is difficult to understand and follow for someone who is not well versed in room acoustics and audiology.